In U.S. Pat. No. 4,019,970, issued 26 Apr. 1977 to the present inventor among others and commonly assigned with the present application, there is described the fabrication of an electrode containing lead-dioxide active material for use in a lead-acid accumulator or storage battery. In that system a supporting body of titanium was pickled in a boiling solution of oxalic acid and then adsorptively coated with a titanium (IV) layer in a treatment bath. This treatment was followed by the anodic coating of the titanium body with PbO.sub.2 in an electrolyte having a given composition.
That system was, in turn, an improvement on the technique described in commonly owned U.S. Pat. No. 3,935,082 which described a process for manufacturing electrodes in which a titanium body was cleaned by pickling and was treated by immersion in a titanium-oxalato complex solution.
The present invention is related to both of these patents in that it also deals with a process for producing electrodes suitable for a variety of electrolytic purposes, especially for lead accumulators or storage batteries and for electrochemical synthesis, the electrodes consisting essentially of a titanium support as described in the aforementioned patents and a deposit or layer of lead-dioxide active material upon this support.
When a titanium support of the type described in these patents is subjected to a cleaning operation or pickling and a surface treatment in the presence of titanium (IV) ions, i.e. tetravalent titanium ions, and the lead dioxide is then applied, problems are encountered as will be discussed below.
Firstly, when an electrode is made from a titanium support and lead dioxide deposit, it is desirable that the electrode have a high cycling life and excellent adhesion of the deposit of lead dioxide to the support, the interface having a minimum resistance.
A strong adhesion of the active material to the support is essential to a high cycling life in the effective use of the electrode, especially in lead-acid or similar storage batteries or accumulators.
In the system of the earlier patents, the lead dioxide deposit is anodically precipitated on the titanium (IV) adsorptive layer. The titanium salt solution could be added to the pickling bath or to a separate surface treatment bath or could be formed in the latter bath.
Experiments have shown that, while the system of the aforementioned patents represents a major advance in the art, nonetheless problems are encountered with the cycling life of the electrodes.